user1 press *0, user2 is transffered to conference 444, then user1 will get dialtone to enter user3 number, after that user1 and 3 are connected,when user1 press **, now this disconnects user1 from the call, but the call will be going on between user2 and user3.

but in N-way, user1 should be able to invite user3 by pressing ** and at the same time user1 should be in call.